Evaluation of the passive particle agglutination test in the serodiagnosis and follow-up of syphilis

A novel pan-proteome array for high-throughput profiling of the humoral response to Treponema pallidum

Given the resurgence of syphilis, research endeavors to improve current assays for serological diagnosis and management of this disease are a priority. A proteome-scale platform for high-throughput profiling of the humoral response to Treponema pallidum (T. pallidum) proteins during infection could identify antigens suitable to ameliorate the performance and capabilities of treponemal tests for syphilis. Additionally, because infection-induced immunity is partially protective, profiling the response to T. pallidum outer membrane proteins (OMPs) could help select vaccine candidates. Therefore, we developed a pan-proteome array (PPA) based on the Nichols and SS14 strain complete proteomes and used it to define the immunoglobulin M (IgM) and IgG humoral response to T. pallidum proteins in sera collected longitudinally from long-term infected rabbits and from rabbits that were infected, treated, and re-infected. We identified antigens that could facilitate early diagnosis and immunity to a core set of OMP that could explain protection upon reinfection.

Comparison of an automated rapid plasma reagin (RPR) test with the conventional RPR card test in syphilis testing

OBJECTIVE

We compared the automated non-treponemal reagin (rapid plasma reagin (RPR)) test with the conventional RPR card test for usefulness in clinical applications.

SETTING

A comparative study of laboratory methods using clinical specimens in a single institute.

PARTICIPANTS

A total of 112 serum samples including 59 Treponema pallidum particle agglutination (TPPA)-positive and 53 TPPA-negative specimens were evaluated.

OUTCOME MEASURES

HiSens Auto RPR LTIA (HBI, Anyang, Korea) was compared with Macro-Vue RPR Card Tests (Becton Dickinson BD Microbiology Systems, Sparks, Maryland, USA). Treponemal-specific tests were performed by Serodia TPPA assay (Fujirebio, Tokyo, Japan). The percentage agreement, κ value and overall sensitivity and specificity of the two RPR tests were compared. Seroconversion rates after treatment were also compared for each RPR test.

RESULTS

The percentage agreement between the two RPR tests was 78.6% (κ 0.565; 95% CI 0.422 to 0.709). Sensitivity and specificity of the automated RPR test relative to the TPPA test was 52.5% (95% CI 39.1% to 65.7%) and 94.3% (95% CI 84.3% to 98.8%), respectively, while the same values for the conventional RPR card test were 86.4% (95% CI 75% to 93.9%) and 94.3% (95% CI 84.3% to 98.8%), respectively. The conventional RPR card test showed overall higher positivity than the automated RPR test, whereas the automated RPR test showed higher seroconversion (43.5%, 10/23) than the conventional RPR card test (4.3%, 1/23) in treated patients.

CONCLUSIONS

The automated RPR test showed overall lower sensitivity than the conventional RPR test based on the treponemal test, but higher seroconversion after treatment. The automated RPR test could be used to monitor treatment response, especially in the reverse screening algorithm in syphilis testing.

Evaluation of a Rapid Immunochromatographic Treponemal Antibody Test Comparing the Treponema Pallidum Particle Agglutination Assay

BACKGROUND

In addition to conventional tests, several methods for detection of treponema-specific antibodies in clinical settings have been recently introduced. We aim to comparatively evaluate a rapid immunochromatographic test (ICT) for Treponema pallidum specific antibody (SD Bioline Syphilis 3.0) and the T. pallidum particle agglutination (TPPA) assay.

METHODS

In all, 132 serum samples from 78 syphilis patients and 54 syphilis-negative controls were analyzed. SD Bioline Syphilis 3.0 test (Standard Diagnostic, Inc., Yongin, Korea) was evaluated and compared to Serodia TPPA assay (Fujirebio, Inc., Tokyo, Japan). All discrepant results between the two assays were repeatedly tested and evaluated by the fluorescent treponemal antibody-absorption (FTA-ABS) assay. Test reproducibility and 95% limit of detection of SD Bioline Syphilis 3.0 were determined across three different lots for seven consecutive days in triplicate. Interference due to autoantibodies and pregnancy was also tested.

RESULTS

Percent agreement between SD Bioline Syphilis 3.0 and TPPA assays was 99.2%. Sensitivity and specificity were 100%, respectively. In TPPA assay, test-to-test, day-to-day, and lot-to-lot variations were not identified until 1:320 titer (eightfold dilutions). There was no interference due to the presence of antinuclear antibodies or samples or pregnancy.

CONCLUSIONS

Percent agreement of SD Syphilis 3.0 and TPPA was very good. Sensitivity and specificity were appropriate for T. pallidum antibody detection. Thus, a rapid ICT could be suitable for syphilis antibody detection.

Sensitivity and specificity of point-of-care rapid combination syphilis-HIV-HCV tests

Background

New rapid point-of-care (POC) tests are being developed that would offer the opportunity to increase screening and treatment of several infections, including syphilis. This study evaluated three of these new rapid POC tests at a site in Southern California.

Methods

Participants were recruited from a testing center in Long Beach, California. A whole blood specimen was used to evaluate the performance of the Dual Path Platform (DPP) Syphilis Screen & Confirm, DPP HIV-Syphilis, and DPP HIV-HCV-Syphilis rapid tests. The gold-standard comparisons were Treponema pallidum passive particle agglutination (TPPA), rapid plasma reagin (RPR), HCV enzyme immunoassay (EIA), and HIV-1/2 EIA.

Results

A total of 948 whole blood specimens were analyzed in this study. The sensitivity of the HIV tests ranged from 95.7–100% and the specificity was 99.7–100%. The sensitivity and specificity of the HCV test were 91.8% and 99.3%, respectively. The treponemal-test sensitivity when compared to TPPA ranged from 44.0–52.7% and specificity was 98.7–99.6%. The non-treponemal test sensitivity and specificity when compared to RPR was 47.8% and 98.9%, respectively. The sensitivity of the Screen & Confirm test improved to 90.0% when cases who were both treponemal and nontreponemal positive were compared to TPPA+/RPR ≥1∶8.

Conclusions

The HIV and HCV on the multi-infection tests showed good performance, but the treponemal and nontreponemal tests had low sensitivity. These results could be due to a low prevalence of active syphilis in the sample population because the sensitivity improved when the gold standard was limited to those more likely to be active cases. Further evaluation of the new syphilis POC tests is required before implementation into testing programs.

Evaluation of new automated syphilis test reagents 'IMMUNOTICLES AUTO3' series: performance, biochemical reactivity, and clinical significance

BACKGROUND

Automated nontreponemal and treponemal test reagents based on the latex agglutination method (immunoticles auto3 RPR: ITA3RPR and immunoticles auto3 TP: ITA3TP) have been developed to improve the issues of conventional manual methods such as their subjectivity, a massive amount of assays, and so on. We evaluated these reagents in regards to their performance, reactivity to antibody isotype, and their clinical significance.

METHODS

ITA3RPR and ITA3TP were measured using a clinical chemistry analyzer. Reactivity to antibody isotype was examined by gel filtration analysis.

RESULTS

ITA3RPR and ITA3TP showed reactivity to both IgM- and IgG-class antibodies and detected early infections. ITA3RPR was verified to show a higher reactivity to IgM-class antibodies than the conventional methods. ITA3RPR correlated with VDRL in the high titer range, and measurement values decreased with treatment. ITA3RPR showed a negative result earlier after treatment than conventional methods. ITA3TP showed high specificity and did not give any false-negative reaction. Significant differences in the measurement values of ITA3RPR between the infective and previous group were verified.

CONCLUSIONS

The double test of ITA3RPR and ITA3TP enables efficient and objective judgment for syphilis diagnosis and treatments, achieving clinical availability.

Comparative evaluation of 15 serological assays for the detection of syphilis infection

Fifteen commercial syphilis kits were assessed against the same moderately sized specimen panel that included 114 serum and plasma specimens from syphilis cases and 249 specimens from unselected blood donors. The 114 specimens from syphilis cases comprised 40 from cases of primary syphilis, 43 from cases of secondary syphilis, 19 from cases of early latent syphilis, and 12 from cases of late latent syphilis. Of the 15 kits, ten were enzyme immunoassays, four were Treponema pallidum haemagglutination assays, and one was a T. pallidum particle agglutination assay. Thirteen of the 15 kits gave final specificities of 100%; the other two kits were repeatedly reactive with one to two specimens. Initial sensitivities ranged from 93.9 to 99.1%. Most variation between kits was observed in results for the groups with untreated primary and treated late latent disease, although the differences were not statistically significant. The comparative data on kit performance derived from this study is useful for examining syphilis testing guidelines and for making informed purchasing decisions.

Evaluation of the Treponema pallidum particle agglutination technique (TP.PA) in the diagnosis of neurosyphilis

The Treponema pallidum particle agglutination technique (TP.PA) was evaluated, in comparison with the Venereal Disease Research Laboratory (VDRL) test, microhemagglutination assay for Treponema pallidum antibodies (MHA-TP), and fluorescent treponemal antibody-ABS (FTA-Abs) test for the diagnosis of neurosyphilis. We have studied 198 cerebrospinal fluid (CSF) samples from patients with syphilis, including neurosyphilis, treated syphilis, and with other neurological manifestations than neurosyphilis. All tests were nonreactive in these last group of patients. In the neurosyphilis patients, sensitivity of the TP.PA was 100%. The performance of this test in CSF from patients with primary syphilis was as good as that of the other tests. In secondary and latent syphilis, the TP.PA results (27 reactive samples/73) were similar to those of the MHA-TP (25 reactive samples/73). In the individuals treated for syphilis, the TP.PA, FTA-Abs, and MHA-TP tests were found to be reactive in eight, six, and eight samples, respectively. In conclusion, it seems that the TP.PA can be used in CSF to diagnose neurosyphilis, although as for other serological tests, interpretation of results should be done in conjunction with other neurosyphilis parameters.

Excellence in sexually transmitted infection (STI) diagnostics: recognition of past successes and strategies for the future

Diagnostic advances do not generally receive the recognition given to prevention and treatment contributions, for the control and management of infectious diseases including sexually transmitted infections (STIs). In order to identify seminal diagnostic contributions over a half century (1950-2000), the Editorial Board of the WHO Sexually Transmitted Diseases Diagnostics Initiative (SDI) Publication Review or "electronic journal club" were asked to nominate their choices of peer-reviewed publications for special recognition. From 43 nominations, 13 were voted by a panel of 25 "experts" as having made the most significant contributions. The 1964 article by Thayer and Martin, which identified a selective media for gonococcal culture, was chosen unanimously by all panel members and is identified as the classic STI diagnostic article for this era.

The laboratory diagnosis of syphilis

Syphilis has several clinical manifestations, making laboratory testing a very important aspect of diagnosis. In North America, many unsuspected cases are discovered by laboratory testing. The etiological agent, Treponema pallidum, cannot be cultured, and there is no single optimal alternative test. Serological testing is the most frequently used approach in the laboratory diagnosis of syphilis. The present paper discusses the various serological and alternative tests currently available along with their limitations, and relates their results to the likely corresponding clinical stage of the disease. The need to use multiple tests is discussed, and the importance of quality control is noted. The complexity of syphilis serology means that the services of reference laboratories and clinical experts are often needed.